Solenoid valves are electro-hydraulic valves that are used to control fluid flow. Solenoid valves are often used, for example, to control pressure of hydraulic fluid in an automatic transmission of an automobile.
Various types of solenoid valves may be used depending on the environment and the purpose of the solenoid valve. One type of solenoid valve is a variable bleed solenoid. Variable bleed solenoids have significant bleed flow throughout most of their pressure range. This flow typically includes contaminants such as metal powder worn from the moving parts, or ferrous debris or general dust in the transmission. Such contaminants can adversely affect the performance of a solenoid if allowed to reach the inner mechanisms of the solenoid. For example, contaminant buildup may restrict armature movement, alter pressure, or alter magnet characteristics within the solenoid.